Nickel electroplating baths

ABSTRACT

Stablized aqueous solutions of aliphatic unsaturated sulfonic acids which contain aliphatic chlorine compounds, and nickelplating baths containing said stabilized aqueous solutions as brighteners.

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[ NICKEL ELECTROPLATIING BATl-IIS [75] Inventors: Walter Schenk, BadDuerkheim;

Friedrich Hovemann, Hockenheim, both of Germany [73] Assignee: BadischeAnilin- & Soda-Fabrih Aktiengesellschalt, Ludwigshafen/Rhein, Germany[22] Filed: Oct. 13, 1972 [21] App]. No.: 297,199

Related US. Application Data [62] Division of Ser. No. l93,996, Oct. 29.1971, Pat. No.

[52] US. Cl. 204/49 [51] lnl. Cl. C23b 5/08, C23b 5/46 PrimaryExaminerG. L. Kaplan Attorney-Richard L. Johnston [57] ABSTRACTStablized aqueous solutions of aliphatic unsaturated sulfonic acidswhich contain aliphatic chlorine compounds, and nickel-plating bathscontaining said stabilized aqueous solutions as brighteners.

5 Claims, N0 Drawings NllCKEL ELECTROPLATING BATES This is a division ofapplication Ser. No. 193,996 filed Oct. 29, 1971, now U.S. Pat. No.3,730,854.

This invention relates to stablized aqueous solutions of aliphaticunsaturated sulfonic acids or salts thereof. Unsaturated aliphaticsulfonic acids, which include for example vinyl sulfonic acid and allylsulfonic acid, are mainly used as brighteners for nickel-plating bathsand as comonomers in the polymerization of, say, acrylonitrile, styrene,acrylic acid, methyl acrylate, methyl methacrylate, maleic acid orN-vinylpyrrolidone.

Their use as brighteners for nickel-plating baths is particularlyimportant and is described in German Printed Applications 1,173,762;1,063,003 and 1,066,069, U.S. Pat. No. 2,800,442, French Patent1,185,579 and German Patent 845,731.

Unsaturated sulfonic acids are used in the form of aqueous solutions ofthe free acids or salts thereof. During storage, these aqueous solutionsform polymerization products, some of which are insoluble in water. Whenunsaturated aliphatic sulfonic acids are used as comonomers, it isnecessary to filter the aqueous solutions immediately before use, whichmeans loss of material. The manufacture of brighteners with unsaturatedaliphatic sulfonic acids and acetylene alcohols, such asbutyne-2-diol-l,4, has the disadvantage that these mixtures also formpolymerization products. Such polymerization products lead to anincrease in the consumption of the brighteners, since the polymericcompounds are insoluble in nickel-plating electrolytes and do not act asbrighteners. One important drawback is that these polymerizationproducts are deposited on the article being nickel-plated and thusinterfere with the plating process.

There are very many ways of stabilizing monomer solutions, which includesolutions of water-soluble unsaturated aliphatic sulfonic acids, bymeans of polymerization inhibitors.

The polymerization inhibitors used are compounds which, due to theirchemical structure,'are capable of absorbing the free radicals whichareliberated during free-radical polymerization. Hitherto, amines,aldehydes, monohydric or polyhydric phenols and ketones have beenregarded as suitable. 1n the case of solutions of aliphatic unsaturatedsulfonic acids or sulfonates there is'the further requirement that thepolymerization inhibitors used should be water-soluble and should notadversely affect the use of sulfonic acids or sulfonates as copolymersor their use as brighteners for nickelplating baths.

It isan object of the invention to provide stable solutions of aliphaticunsaturated sulfonic acids orsalts thereof which contain inhibitorswhich do not cause discoloration. It is a further object to providesolutions from which copolymers of excellent color may be obtained. Yetanother object is to provide aqueous solutions of aliphatic unsaturatedsulfonic acids which may be used, after storage, in nickel-plating bathswithout filtration of said aqueous solutions being necessary. Finally itis an important object of the invention to enable such stabilizedsolutions to be used as bighteners in nickel-plating baths to obtainnon-discolored bright nickel deposits without impairing theelectroplating action.

1n accordance with the invention, these and other objects and advantagesare achieved by stabilized aqueous solutions of aliphatic unsaturatedsulfonic acids or salts thereof which contain an aliphatic saturatedchlorine compound of from one to four carbon atoms in a concentration offrom 0.2 to 8 percent by weight, based on the pure sulfonic acid or saltthereof.

The chloride compounds to be used are aliphatic, saturated chlorinecompounds having from 1 to 4 chlorine atoms associated with homopolarbonds and containing from one to four carbon atoms. Specific example aremethylene chloride, chloroform, carbon tetrachloride, l-chloroethane,1,1-dichloroethane, 1,1,1-

trichloroethane, ethylene chloride, 1,1 ,2,2- tetrachloroethane,1,1-dichloropropane, l ,2- dichloropropane, l,3'dich1oropropane, 1,2,3-trichloropropane, l ,l ,2-trichloropropane, l-

chlorobutane, 2-chlorobutane and 3-chlorobutane. We prefer to usemethylene chloride, 1,2-ethylene chloride and 1,2-dichloropropane,ethylene chloride being particularly important commercially.

Water-soluble unsaturated aliphatic sulfonic acids are those containingtwo or three carbon atoms, such as allyl sulfonic acid and vinylsulfonic acid, the latter being preferred.

The salts thereof are equally suitable and indeed are to be preferredowing to their better solubility in water. Suitable salts are the alkalimetal salts, for example the sodium and potassium salts, and thealkaline earth metal salts such as the calcium and magnesium salts, andheavy metal salts, such as the iron, nickel and cobalt salts. The alkalimetal salts are preferred, the sodium salts being particularly importantcommercially.

The aqueous solutions conveniently contain from 10 to 75 and preferablyfrom to 60 percent by weight of sulfonic acids or salts thereof based onthe aqueous solution. Commercially available forms are to percentsolutions. To these solutions there are added to chlorine compoundsproposed by the invention in amounts of from 0.2 to 0.8 percent andpreferably from 0.32 to 0.8 percent by weight of the pure sulfonic acidor salt thereof, depending on the concentration of the solution.

The unsaturated aliphatic sulfonic acids may be read ilycopolymerizedwith known monomers in the aqueous solutions stabilized in the mannerproposed by the present invention. No discoloration of the copolymers orreaction delays can be observed.

When the solutions of the invention are to be used in nickel-platingbaths, the aqueous solution stabilized in the manner proposed by theinvention is conveniently added to a Watts nickel electrolyte in anamount ranging from 0.1 to 0.3 percent by weight of the nickelelectrolyte, which also contains from about 0.01 to 0.1 percent of itsweight of an acetylene alcohol as convenient brightener, for examplehexyne-3-diol-2,5, 1,4-bis-(2- hydroxyethoxy)-2-butyne or, preferably,butyne-2- diol'l,4.

Highly satisfactory results are obtained even when the added brightenerconsists of an aqueous solution of unsaturated aliphatic sulfonic acidswhich has been stored for a long time, this being due to thestabilization achieved in the present invention.

In the following Examples, the difference between the conventionalsolutions and those of the invention is illustrated.

EXAMPLE 1 1,000 parts of a 25 percent aqueous solution of the sodiumsalt of vinyl sulfonate and containing no further additive were placedin a glass tube, which was sealed by fusion of the glass to preventevaporation of the water. The whole was then stored at 40C for 120 days.The hydrogenation iodine number fell from 50 to 35 and the color changedfrom pale yellow to brown.

To 1,000 parts of a 25 percent aqueous solution of the sodium salt ofvinyl sulfonate there were added parts of ethylene chloride. Theethylene chloride dissolved completely to form a clear solution. Thissolution was placed in a glass tube, which was sealed by fusion of theglass to prevent evaporation losses. The

. whole was stored at 40C for hydrogenation iodine number remained at 50and the color also remained unchanged.

EXAMPLE 2 1,000 parts of a 25 percent aqueous solution of the sodiumsalt of vinyl sulfonate were placed in a quartz bulb and irradiated witha 300 w mercury vapor lamp. Whereas the hydrogenation iodine number ofthe unstabilized product fell from 50 to 36 and its color changed frompale yellow to dark brown, the iodine number of a sample containing 10parts of ethylene chloride fell from 50 to only 48 and its color changedfrom pale yellow to yellow when subjected to the same conditions.

ln a test carried out under the same conditions, 10 parts ofhydroquinone were used in place of the 10 parts of ethylene chloride.Immediately, the color of the product changed to dark brown and thehydrogenation iodine number fell from 50 to 45.

EXAMPLE 3 Ten parts of butyne-2-diol-l,4 were dissolved in 40 parts of a25 percent vinyl sulfonate solution. A parallel specimen was prepared inlike manner except that 0.5 percent of ethylene chloride was added tothe vinyl sulfonate solution. About parts of each solution were placedin separate thick-walled glass tubes each containing a glass spherehaving a diameter equal to the internal diameter of the glass tube,whereupon the tubes were sealed by fusion. At the commencement of theexperiment the falling time of the;glass spheres was 7.5 seconds. Afterstorage of the tubes at room temperature for 4 weeks, the falling timein the unstabilized vinyl sulfonate solution was 8.9 seconds, whilst itwas 7.6 seconds in the stabilized solution. This increase in viscosityis due to the formation of polymerization products. Visual examinationof the brighteners also revealed that no precipitates were present inthe tube containing the stabilized vinyl sulfonate but that yellowishbrown precipitates were present in the tube containing the unstabilizedvinyl sulfonate solution.

EXAMPLE 4 A Watts nickel electrolyte of the following composition:

300 g/l of nickel sulfate (NiSO -7H O) 45 g/l of nickel chloride (NiCl-6H 41 g/l of boric acid (H was prepared, and 1.2 g/l of the abovebrighteners were added. Degreased brass plates of grade Ms 63 werenickel-plated therein at 60C in a parallel cell at a current density of5 amps/dm Bright deposits having a flawless mirror finish were obtainedbut only when stabilized vinyl sulfonate was used.

We claim:

1. An aqueous Watts nickel electroplating electrolyte comprising 0.01 to0.1 percent by wt. of an acetylenic alcohol and 0.1 to 0.3 percent bywt. of an additive composition comprising 1075 percent by wt. of anunsaturated sulfonic acid or salts thereof and 0.2 to 0.8 percent by wt.(based on the sulfonic acid or salts thereof) of a saturated aliphaticchlorine compound having from one to four carbon atoms and from one tofour chlorine atoms in the molecule.

2. Nickel plating baths as claimed in claim 1 in which said solutioncontains salts of unsaturated aliphatic sulfonic acids.

3. Nickel plating baths as claimed in claim 1 in which said saturatedaliphatic chlorine compound is methylene chloride, chloroform, carbontetrachloride, 1-

chloroethane, 1,1-dichloroethane, 1,1,1- trichloroethane, ethylenechloride, l,1,2,2- tetrachloroethane, 1,1-dichloropropane, 1,2-dichloropropane, 1,3-dichloropropane, 1,2,3- trichloropropane, 1,1,E-trichloropropane, 1-

chlorobutane, 2-chlorobutane, 3-chlorobutane or mixtures thereof.

4. Nickel plating baths as claimed in claim 1 in which said saturatedaliphatic chlorine compound is methylene chloride ethylene chloride or 1,2- dichloropropa'ne.

5. Nickel plating baths as claimed in claim 1 in which said saturatedaliphatic chlorine compound is ethylene chloride.

UfiITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. vDated December 18, 1973 Walter Sc'henk et a1. Inventor(s) It iscertified that error appears in the above-identified patent and thatsaid Letters Patent arehereby corrected as shown below:

Columh 4', line 10, "(NiC1 '6H should read --(NiCl 6H' O) line 43,before "ethylene" insert a comma.

Signed and sealed this 26th day of November 1974.

(SEAL) Attest:

c. MARSHALL DANN McCOY M. GIBSON JR.

Commissioner of Patents Attesting- Officer USCOMM-DC 60376-P69 F ORMPO-1050 HO-69)- u.s. covnnnsn PRINTING orncz: 93 o

2. Nickel plating baths as claimed in claim 1 in which said solutioncontains salts of unsaturated aliphatic sulfonic acids.
 3. Nickelplating baths as claimed in claim 1 in which said saturated aliphaticchlorine compound is methylene chloride, chloroform, carbontetrachloride, 1-chloroethane, 1,1-dichloroethane,1,1,1-trichloroethane, ethylene chloride, 1,1,2, 2-tetrachloroethane,1,1-diChloropropane, 1,2-dichloropropane, 1, 3-dichloropropane,1,2,3-trichloropropane, 1,1,2-trichloropropane, 1-chlorobutane,2-chlorobutane, 3-chlorobutane or mixtures thereof.
 4. Nickel platingbaths as claimed in claim 1 in which said saturated aliphatic chlorinecompound is methylene chloride ethylene chloride or 1,2-dichloropropane.5. Nickel plating baths as claimed in claim 1 in which said saturatedaliphatic chlorine compound is ethylene chloride.